Genetic Testing in 2014 - Children`s National Health System

Genetic Testing in 2014
Brendan Lanpher, MD
Children’s National Health System
Washington, DC
Conflict of Interest Disclosure
Dr. Lanpher has no financial interests, arrangements, affiliations, or any bias with any of the
corporate organizations offering financial support or educational grants for this program.
Why is this Important
Genetic Testing expanding exponentially
So is the cost
Insurance coverage spotty and unpredictable
Results complex, unclear and may be misleading
Why Do Any Test
Determine diagnosis
Determine treatment
Determine prognosis
Determine risk
Determine recurrence/family risk
Genetic testing can help with all
Two Types of Testing
Reactive
• Something is wrong with the patient and you want to find out what.
• Useful to know what else might go wrong
• Useful to know who else might have the same thing.
Predictive or Proactive
• Want to know if something might go wrong or how someone will
respond to an external stimulus (drugs)
• Very very early stages of utility
• Most advanced is pharmacogenetics
• Does not always produce actionable data
• Massive amounts of work before this is useful.
Test Selection Factors
Information quality
Cost
Utility of information
Ability to process information
Time to result
Testing: It’s a matter of resolution
Karyotype or Chromosome Analysis is low resolution
but very well established.
Great for trisomies,
rearrangements, large missing pieces. Can get fast. If
testing all patients seen in genetics about 3-5% yield
Chromosome Microarray (CGH) is much higher
resolution (latest 1 million probes). Very well
established.
Great for trisomies, and small
duplications and deletions. If testing all patients
seen in genetics about 26% yield.
In nonsyndromic developmental delay about 10-15%
Sequence Analysis very useful in targeted situations of
suspected genes. Usually confirmatory. Newer whole
exome sequencing returns about 5,000 positive results
per patient. Whole genome about 10,000,000. Slow.
Data processing most complex part.
Cytogenetic Resolution
1 kb = 1,000 base pairs
1Mb = 1,000,000 base pairs
Metaphase karyotype = 5-10Mb
High resolution karyotype = 3-4Mb
FISH = 30-40 kb
CMA= 1-5 kb
Consensus Statement: Chromosomal
Microarray Is a First-Tier Clinical
Diagnostic Test for Individuals with
Developmental Disabilities or Congenital
Anomalies (AJHG, 2010)
Chromsome Microarray
For patients with Developmental delay (including autism) the positive hit rate
is 10-20%
Testing costs about $1500-$3000 and takes about 4 weeks to get back (getting
better)
Many Variants of Unknown Signficance (VOUS) which require interpretation.
About 20% but dropping.
Will not detect balanced rearrangements.
Variable detection of mosaicism
Is now the standard of care in genetics clinics for first line workup of Multiple
Congenital Anomalies, DD, Autism, etc.
Complex results - CMA
Clinical History:Imperforate anus, multiple congenital anomalies
CYTOGENETIC RESULT: arr[hg19]2q21.1(131,477,947-131,933,576)x1
INTERPRETATION and COMMENTS: Copy Number Variation Identified: Unclear Clinical
Significance (Interpret with caution). Genes involved: GPR148, AMER3, ARHGEF4, FAM168B,
PLEKHB2 (http://www.ncbi.nlm.nih.gov/omim) An approximately 456 kb loss on chromosome 2
at 2q21.1 was detected. This deletion has recently been described as a rare, recurrent deletion
that may be associated with developmental delay (DD)/intellectual disability (ID), ADHD,
epilepsy and other neurobehavioral abnormalities [Dharmadhikari AV, et al., Hum Mol Genet.
2012 Aug 1;21(15):3345-55. doi: 10.1093/hmg/dds166. Epub 2012 Apr 27. PMID:22543972].
However, the clinical significance of this deletion in a newborn is unclear and ongoing genotypephenotype correlation is recommended.
Importance of Definitions
POLYMORPHISM vs MUTATION vs VARIANT
•Old Common usage: >1% in the population is a polymorphism
• Polys are “non-deleterious”
•Mutations are supposed to cause molecular pathophysiology.
•The lines are blurring:
• common changes have deleterious effects in one situation and
beneficial in another.
• Example: hemochromatosis (c282y) change found in 10% of caucasian
population. Affects iron storage
•Common report terminology is Variant with a comment on its effect.
•
If unknown then “Variant of Unknown Significance
Challenge: informatics
If you want to store the data in a raw format for later re-analysis, you're
looking at between 2 and 30 terabytes (one terabyte = 1,000
gigabytes). A much more user-friendly format, though, would be as a
file containing each and every DNA letter in your genome, which would
take up around 1.5 gigabytes
Limitations of Genetic Testing
Variable penetrance. Changes may not always lead to
disease.
Software systems for “friend or foe” determination of
sequence variation are only fair.
Existing tests often look for the most common
mutations, some disease causing mutations will not be
detected in different ethnic groups.
Small chance of errors in testing procedure.
Testing is not always matched by treatment.
Functional Testing as a Surrogate for DNA testing
Biochemistry (blood/urine/CSF levels)
Newborn Screening
Enzyme function
Tissue staining
Protein Characteristics
A good exam.
Advantages
• One test many mutants
• Biologic relevance is clear
Example
• High ammonia reflects 8 urea cycle genes and at least 6 organic acid genes
Whole Exome (typically 18-22K genes)
Sounds great right?
Nature Genetics 2010 (N Genetics 42, 969-72, 2010)
•
•
•
•
200 normal adult Danes
18,654 genes sequenced per individual
121,870 single nucleotide variations
53,081 were coding changes
The biggest cost/burden of whole exome is interpretation and
informatics. Non-deleterious changes vary from population to
population. Expect up to 5000 variants per individual.
Whole Exome Sequencing – In Practice
Need trios (both parents and patient)
Results never completely normal
Most often with possible answers, rarely definite
• Functional studies may not be possible
Significant issues with incidental findings
• Adult onset disease
• Cancer, cardiac, neurodegenerative
•
Carrier status
Specific Testing in Practice: Ground Rules
A Genetics Consult is cheaper than any one genetic test. ($300 vs $310,000+)
Genetic counseling must be done before and after the testing. Manage
expectations (takes time!)
Since they take awhile to return make sure someone is tracking the results.
(return time is months)
Anticipate that the answer may be ambiguous. The reports are purposefully
done this way. (average review time >2-3 hrs)
Fill out the clinical profile for the test. This will greatly help interpretation by
the lab.
Remember that a negative test does not completely rule any genetic disease
How Can We Help
Children’s National Genetics and Metabolism
• 202-476-6287
• 13 Medical Geneticists (11 double in Biochemical)
• 15 Genetic Counselors
• Tracking Following Counseling Diagnosis Testing
• Genetics@childrensnational.org
Personalized Medicine
The Promise
•
•
•
•
Determine health risk
Drug metabolism
Best care practices
Better health
But
• Needs correlation between DNA
sequence and risk
• What is actionable?
• Population and environment specific.
• Ethics
Not there yet.
Personalized Medicine by the Numbers
Growth
• 13 prominent examples of personalized medicine drugs, treatments and
diagnostics products available in 2006
• 72 prominent examples of personalized medicine drugs, treatments and
diagnostics products available in 2011
Drug Use
• 1% of marketed drugs have a companion diagnostic
• 10 % of marketed drugs inform or recommend genetic testing for optimal
treatment
• 33 pharmacogenomic biomarkers are included on FDA-approved drug
labels
Personalized Medicine Coalition. The Case for Personalized Medicine. 2011
Economics
34% reduction in chemotherapy use would occur if women with
breast cancer receive a genetic test prior to treatment
17,000 strokes could be prevented each year if a genetic test is
used to properly dose the blood thinner warfarin
$604,000,000 annual cost savings to the health care system if
patients with metastatic colorectal cancer receive a genetic test
for the KRAS gene prior to treatment
Personalized Medicine Coalition. The Case for Personalized Medicine. 2011
RECREATIONAL GENETICS
Consumer Based Testing
Direct to Consumer
•
23andMe, KnowMe, Navigenics
Nutrigenomics
•
Sciona, Genelex, Market America, Suracell
Ancestry Testing
• Genographic,GeneTree, DNAPrint
Skin and Hair Care
• HairDx, Dermagenetics
Canine Breed Analysis
Questions?